The effects of vegetation distribution pattern on overland flow

Abstract Soil erosion is a major environmental problem. Vegetation, on the other hand, plays an important role in controlling soil erosion. The goal of the study is to examine the effects of the distribution pattern of vegetation on water flow. The vegetation parameters involved included the direction of plant rows, plant stem diameter and row spacing. To study how vegetation affects the flow of water on slopes, flume simulation experiments were conducted using three different plant row directions, three different plant diameters and three row spacing. Experimental slope is fixed, slope ratio of 1.0%. The hydraulic characteristics of the slope under the three vegetation distribution patterns are explored. The results showed that the pattern of vegetation distribution significantly affected the resistance of vegetation to water flow and pattern on this slope. When the angle (θ) between plant row and water flow directions decreased, the plant diameter (d) increased, or the row spacing (a × a) decreased, the Darcy–Weisbach resistance coefficient (f) for water flow became larger. Simultaneously, the Reynolds and Froude numbers (Re and Fr) both became smaller. In experimental procedure condition, the change rate of f, Re and Fr were analysed by linear regression, the θ decreased every 10°, the average increase rate of f was 6.6%, the average decrease rate of Re and Fr were 2.0 and 3.0%. The d increased every 0.001 m, the average increase rate of f was 41.6%, the average decrease rate of Re and Fr were 11.2 and 12.2%. The a × a decreased every 0.01 m, the average increase rate of f was 45.2%, the average decrease rate of Re and Fr were 11.7 and 10.7%. The flow depth h increased every 0.01 m, the average increase rate of f and Re were 13.6 and 25.2%, and the average decrease rate of Fr was 10.4%. The experimental procedure results will be valuable for not only revealing the hydraulic characteristics of flow over vegetation land, but also the optimisation of the distribution of vegetation on a slope.